Solar energy is a renewable energy source that has gained significant worldwide popularity due to the recognized limitations of fossil fuels and safety concerns of nuclear fuels. The photovoltaic (PV) solar energy demand has grown at least 25% per annum over the past 15 years. Worldwide photovoltaic installations increased by 1460 MW (Megawatt) in 2005, up from 1,086 MW installed during the previous year (representing a 34% yearly increase) and compared to 21 MW in 1985.
Most growth in the field of solar energy has focused on solar modules fixed on top of an existing roof. Rooftops provide direct exposure of solar radiation to a solar cell and structural support for photovoltaic devices. Despite increased growth, the widespread use of conventional roof-mounted solar modules has been limited by their difficulty and cost of installation, lack of aesthetic appeal, and especially their low conversion efficiency.
Most conventional roof-mounted solar modules are constructed largely of glass enclosures designed to protect the fragile silicon solar cells. These modules are complex systems comprising separate mechanical and electrical interconnections that are then mounted into existing rooftops, requiring significant installation time and skill. Available modules are also invasive in the aesthetics of homes and commercial buildings, resulting in limited use. A few manufacturers have fabricated more aesthetically pleasing and less obstructive solutions, but the systems are not price competitive largely due to installation difficulties and poor total area efficiency. Lower module efficiency levels are correlated to higher photovoltaic system costs because a greater module area is required for a given energy demand.
The efficiency of converting light into electricity for a typical crystalline-silicon roof-mounted solar cell is approximately 13%. Some systems have seen efficiency increases (up to 18-20%) by modifications such as the use of anti-reflective glass on the cell surface to decrease optical reflection, use of textured glass on the cell surface to increase light trapping, and the use of improved materials like thin film silicon or germanium alloy. Despite these improvements, solar cell conversion efficiency remains limited, in part, by high solar cell temperatures. The efficiency of a photovoltaic device decreases as the temperature increases. Part of the energy radiated onto the cell is converted to heat, which limits the electrical energy output and overall conversion efficiency of the cell. Fabrication of a system capable of removing heat from the photovoltaic cell would greatly increase total efficiency.
There is significant interest in and need for a photovoltaic module that addresses the above problems.